The communications industry is rapidly changing to adjust to emerging technologies and ever increasing customer demand. This customer demand for new applications and increased performance of existing applications is driving communications network and system providers to employ networks and systems having greater speed and capacity (e.g., greater bandwidth). In trying to achieve these goals, a common approach taken by many communications providers is to use packet switching technology. Increasingly, public and private communications networks are being built and expanded using various packet technologies, such as Internet Protocol (IP). Note, nothing described or referenced in this document is admitted as prior art to this application unless explicitly so stated.
Packet switching devices have evolved from devices where each device represents a single router or bridge, to devices that support multiple “forwarding contexts.” As used herein, forwarding contexts include, but are not limited, to virtual routers, logical routers, and/or virtual private networks. Each forwarding context maintains or is associated with packet forwarding information relevant to itself. For example, two logical routers might be housed in the same physical device, but these different forwarding contexts will maintain separate routing tables and forwarding information based for use in processing and forwarding packets.
Of course, this processing of packets in one forwarding context may determine that certain packets should be communicated to a different forwarding context. In the past, this has meant that the packet should be sent to a different packet switching device. However, today, it is possible that these different forwarding contexts are housed in a same physical packet switch, such as in different logical or virtual routers of a single physical router.
One prior approach used to communicate packets between two forwarding contexts, especially between logical routers (i.e., where each line card only belongs to a single forwarding context) uses physical cables to connect different forwarding contexts with each other, which requires a technician to correctly connect a physical cables for each pair of forwarding contexts.
Another prior approach used in a physical router avoids the overhead of the previously described prior approach by combining forwarding information belonging to multiple virtual forwarding contexts, which effectively blurs the physical structure of the physical router. For example, by determining a forwarding information base using information from multiple forwarding contexts, a packet to be forwarded from an ingress port of the physical router directly to an egress port of the physical router even if the egress port is associated with a different forwarding context than the ingress port.